Document Type : Research Paper
Homi Bhabha National Institute, Anushaktinagar, Mumbai - 400094
Desalination & Membrane Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai - 400085
Powder Metallurgy Division, Materials Group, Bhabha Atomic Research Centre, Vashi Complex, Navi Mumbai - 400705
Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai - 400085
Product Development Division, Bhabha Atomic Research Centre, Trombay, Mumbai – 400085
Hydrogen separation from purge gas of ammonia production unit is an important step for maintaining the desired composition of gas in ammonia synthesis reactor, with an overall objective of helium concentration. Metal membranes, owing to high selectivity (typically >10,000) for hydrogen, are potential candidates for separation of hydrogen from un-reacted hydrogen-helium mixture. In this work, we report for the first time, fabrication, characterization and testing of composite Vanadium-Iron (V: 95 mol% - Fe: 5 mol%) metal membrane for separation of hydrogen - helium gas mixture, and CFD simulation of V-Fe membrane permeator. The clay-alumina support tubes were fabricated with optimized composition of 8% clay and 92% alumina, sintered at 1400 ºC. At optimized composition, average pore size of support was found to be 1.5 μm with a porosity of ~ 37%. The hydrogen permeance of V-Fe membrane was found to be ~ 300 GPU with no helium detected in the permeate. CFD simulation studies were carried out for single-tube (78.5 cm2) as well as scaled-up membrane permeator having a total membrane area of 0.22 m2. Optimized set of parameters to achieve a hydrogen recovery of >95% (flow rate: 7.17 kg/s) was found to be: Reynolds number: 8.28 × 10-3, Feed-side pressure: 5 bar, Annular space for feed flow: 28.98 mm. The study provides valuable inputs for design and development of commercial metal membrane permeator for separation of hydrogen from the helium present in purge gas of ammonia production unit.